Conventionally, glass sheets are subjected to various surface treatments for the purpose of giving the glass sheets characteristics suitable for the intended use. For example, a technique of forming a thin film having a high transmittance on a surface of a glass sheet is known as one method for obtaining a glass sheet having a high transmittance. For example, Patent Literature 1 describes a glass sheet including a thin film whose main component is silicon nitride and that contains at least one of carbon and hydrogen. In addition, Patent Literature 2 describes a glass sheet having an improved transmittance provided by a thin film having a multi-layer structure in which one of the layers is a vanadium oxide layer having tungsten and fluorine added thereto. Furthermore, Patent Literature 3 proposes that when a thin film such as a metal oxide film is formed on a surface of a glass sheet in order to obtain a glass sheet having a high transmittance, dealkalization is carried out as a pretreatment for the purpose of preventing alteration of the thin film.
As another example of a method for increasing the transmittance of a glass sheet, Patent Literature 4 proposes a method relating to a glass sheet formed by a float process, the method including removing a predetermined thickness of an outermost surface portion of the bottom side of the glass sheet so as to remove a layer containing tin cations. This method makes it possible to obtain a glass sheet that exhibits a high transmittance intrinsic to the glass composition.
Depending on the intended use, surface treatments of glass are performed not only by the above methods but also by other various methods, such as a method of obtaining glass having a dense surface structure (Patent Literature 5) and a method of obtaining a glass sheet having a high transmittance for visible light by providing a plurality of depressions in a glass surface (Patent Literature 6).